Feeding mechanism for plastic extrusion molding machines



I. B. LADWYER May 23, 1939.

FEEDING MECHANISM FdR PLASTIC EXTRUSION MOLDING MACHINES Filed April 26, .1937 2 Sheets-Sheet 1 INVENTOR MW 5. LAWYER A TTORNEYS y 23, 1939- l. B. LAWYER 2,159,559

' FEEDING MECHANISM FOR PLASTIC EXTRUSION MOLDING MACHINES Filed April 26, 1957 2 shqe-ts sheet 2 //VVENTOR MM 8. LAWYER 4 ATTORNEYS Patented May 23, 1939 FEED ING MECHANISM FOR PLASTIC EX- TRUSION MOLDING MACHINES Ira B. Lawyer, Mount Gilead, Ohio, asaignor to The Hydraulic Press Corp. Inc.. Wilmington, Del., a corporation of Delaware Application April 26, 1937, Serial No. 138,944

9 Claims.

This invention relates to plastic extrusion molding machines, and in particular, to feeding devices for such machines.v

One object of this invention is to provide a l motor-driven feeding device wherein a positively driven feeding member cooperates with gravity in feeding the material.

Another object is to provide a motor-driven feeding device wherein the feeding mechanism 10 is operated electrically and controlled by the energization and deenergization of an electric circuit. Another object is to provide a feeding and injection device for a plastic extrusion molding machine, wherein the injecting member operates an electric switch which controlsthe energization of a circuit operating the feeding member of the feeding mechanism.

Anothervobject is to provide a feeding and in jection device, wherein a feed screw supplies material to the injection chamber and is operated by a motor in a circuit controlled by a switch adapted to be shifted in response to the travel of the injection member.

Another object is to provide a feeding'and ina 25 jection device, as described in the preceding paragraph, wherein means is provided for supplying an amount of material slightly in excess of the required amount, and enabling the feeding mechanism to be deenergized and rendered inoperaao tive when the accumulation of material in the injector exceeds a predetermined amount. Another object is to provide a feeding and injection device, as described above, wherein the,

trols the length of time, and hence, the quantity of material which the feeding member. feeds to the injector.

45 Another object is to provide a feeding and injection device, wherein the feeding member, such as a' screw, feeds the material into a vertical 'chute opening into the injection chamber, in such a manner that excess material may accumu- 50 late in the chute.

In the drawings:

Figure l is a diagrammatic view, partly in section, ofthe feeding and injection device of this General construction In general, the feeding and injection device of this invention consists of an injector having a chamber with an injection plunger reciprocating therein, this plunger being preferably oper ated by fluid pressure. Opening into the injection chamber is a vertical passageway or chute communicating with a substantially horizontal feeding chamber having a feed screw rotated therein by means of an electric motor. A molding material hopper opens into the feeding chamber. The feeding motor is controlledby a magnetic motor switch, which in turn, is energized by the cooperative working of an electrical timing switch and a limit switch actuated in response to the travel of the injection plunger. This limit switch is normally open, and is closed when the injection plunger reaches a predetermined position, thereby energizing the motor circuit and starting the timing device, which after a predetermined period, opens the circuit and cleenergizes the motor.

Injector construction Referring to the drawings in detail, Figure 1 shows the feeding and injection device of this invention as including an injector, generally des-- ignated i0, having an injector chamber H with. a spindle-shaped plastic material deflector i2, spaced from the chamber enlargement i3 by the spacing portions i4. Beyond the deflector I2 and the chamber enlargement i3 there is mounted a nozzle it having a tip it with an aperture ii for the extrusion of the plastic molding material. The injector ill is heated by any suitable means (not shown), such as byan electrical heating coil or by a hollow chamber or jacket containing circulating hot oil.

The injector chamber ii is arranged to receive an injection plunger l8, continuing in an 5 enlarged piston rod i! with a piston head 20 mounted thereon and reciprocating in a cylinder 2| with a bore 22, reached by the ports 23 and 24, respectively. Mounted between the piston rod i9 and the injection plunger i8 is a cam mem- 50 her 25, secured thereto by the collars 26 and 21. The latter may be threaded upon the plunger l8, or secured thereto by set screws, or in any other convenient way. Arranged to be engaged by the cam member 25 when the injection plunger l3 nears the forward limit of its stroke is a limit switch 23, having a switch arm 29 mounted upon a fixed portion 33 ofthe machine The limit switch 23 is of a normally open type adapted to be closed when the switch arm 29 is engaged by the cam member 25.

Feeding mechanism The feeding .mechanism consists of a substantially vertical chute 3| opening, as at 32, into the injection chamber and having a feed casing 33 secured thereto near the top thereof, as at 34 (Figure 3). The feed casing 33 contains a bore or chamber 35 having an inlet 33 opening into a conical receiver 31 for a funnel-shaped hopper 33. Operating in the feed chamber 35 is a feed screw 39 having a reduced shaft 43 supported by an antifriction bearing 4|, having an oil check device 42 associated therewith. The shaft 43 terminates in the socket 43 of the motor assembly output shaft 44 and is interconnected therewith by the pin 45. The motor assembly 43 consists of an electric motor 41 and reduction gearing 43, causing the output shaft 44 to rotate at a greatly reduced speed in comparison with the speed of the motor itself.

Electrical system The electrical circuit for actuating the feeding motor 41 (Figure 2) consists of a four-pole magnetic switch 49, controlling the energization of the motor 41, the limit switch 23, already described, and an electrical timing switch 53 interconnected by appropriate wiring. The motor starting switch -49 includes an operating coil 5| having an armature 52 interconnecting and actuating the switch, blades 53, 54, 55 and 53, and closing the switch 49 when the operating coil 5| is energized. The timing switch 53 consists of a timing motor 51, main contacts, generally designated 53, and auxiliary contacts, generally designated 59, and a coil 33 which operates a clutch (not shown) holding the main contacts 53 open, once they have opened, until the coil 33 is deenergized. Whenthis occurs the timing switch 53 automatically resets itself,

ready for the next operation.

The timing switch motor 51 is a synchronous motor which, in an adjustable predetermined time after it has started, opens the main contacts 53. The auxiliary contacts 59 open to stop the motor when the maximum time cycle for which the timing switch 53 is designed is reached, thereby preventing damage to the instrument. The tim- Operation If it is desired to make an injection and feeding operation,pressure fluid is admitted through the port 23 (Figure 1) into the cylinder bore 22, where it causes the piston head 23 and the piston rod 2| to move to the left, causing the injection plunger l3 to make an injection stroke. This forces the plasticinjection material within the injection chamber out through the enlargement l3, past the deflector l2 and through the aperture ll of the injector nozzle tip l3. When the injection plunger l3 nears the end of its working stroke, the

cam engages and shiftsthe switch arm 23, closing the switch blade of the limit switch 28 upon its contacts.

This action energizes the operating coil 5| of the magnetic switch, 49 from the power line 33, through the now closed limit switch 28, the operating coil 5|, the main contacts 53 of the timing switch 53, thence to the power line 3|. .The operating coil 5| thereupon shifts the armature 52 and clcses the switch blades 53 to 53, inclusive. The closing of the switch blades 53,54 and 55 energizes and starts the feeding motor 41 so that the feed screw 39 starts rotation. The molding material contained in the hopper 33 will therefore be forced to the left, into the vertical chute 3|, and through the port 32, into the injector chamber I when the plunger I3 is retracted.

The timing motor 51 of the timing switch 53 is started by the closing of the switch blade 53, the latter action energizing the timing motor circuitfrom the line 33, through the switch blade 53, the auxiliary contacts 59, the timing motor 51 and the -line running back to the power line 3|. The timing motor runs for the length of time for which the timing switch 53 is set, and then opens the main contacts 58 thereof. This action breaks the circuit beginning at the power line 33, through the switch blade 53, the operating coil 5|, the main contacts 58 of the timing switch 53 and the line running back to the power line 6|.

The deenergization of the operating coil 5| permits the switch blades 53 to 53, inclusive, to fly open, under the influence of any suitable means, such as a spring (not shown), thereby deenrgizing and stopping the feed motor '41. In case the limit switch 23 is still held closed the coil 33 of the timing switch prevents the timing switch 53 from being reset until the reverse movement of the injection plunger 3 shifts the cam 25 and releases the switch arm 29 of the limit switch 28.

By adjusting the timing switch the number of revolutions of the feed screw may be controlled, thereby controlling the amount of material measured out atone cycle of operation. The timing switch 23 may be adjusted in position alongthe fixed portion 3.3 so that it can be actuated at any desired location. The timing switch 53 is preferably adjusted in such a manner that slightly more material is fed at asingle cycle of operation into the injection chamber than can be used at one stroke'of the injector plunger I8. Accordingly, the injector chamber |l gradually fills up with material until the injection plunger i3 does not move inward far enough to permit the cam 25 to close the limit switch 23. When this occurs the feed motor circuit is not energized, hence, the feed motor 41 will not be operated and one feeding operation will be missed.

This skip-stroke feeding arrangement thereby compensates for the slight over-feed which has caused a surplus of material to accumulate. In

this way the injector chamber II is constantly assured of an adequate supply of injection material by the provision of a. surplus amount fed thereto, and yet an accumulation of this surplus material is taken care of by the skip-feed arrangement.

It will be understoodthat I desire to comprehend within this invention such modifications as come within the scope of the claims and the invention.

Having thus fully described my invention, what .I claim as new and desire. to secure by Letters Patent, is:

1. In a feeding and injecting device, an inaisass'a jector chamber, an injection member-therein, a substantially --vertical passageway opening into said injector chamber, a feeding chamber connected to said passageway, a movable feeding member in said feeding chamber, a motor operatively connected to said feeding member for moving said feeding member, said motorincluding a motor energizing circuit, means for energizing said circuit, and a timing device responsive to the expiration of a predetermined period of time after the energization of said motor circut for deenergizing said motor circuit.

2. In a feeding and injecting device, an injector chamber, an injection member therein, a substantially vertical passageway opening into said injector chamber, a feeding chamber connected to said passageway, a movable feeding .member in said feeding chamber, a motor operatively connected to said feeding member for moving said feeding member, said motor including a motor energizing circuit, means for energizing said circuit, a timing device responsive to the expiration of a predetermined period of time after the energization of said motor circuit for deen'ergizing said motor circuit, and a limit switch responsive to the travel-of said injection member for controlling the 'energization of said motor circuit.

3. In a feeding and injecting device, an injector chamber, an injection member therein, 'a substan tially vertical passageway opening into said injector chamber, a feeding chamber connected to said passageway, a movable feeding member in said feeding chamber, a motor operatively connected to said feeding member for moving said feeding member, said motor including a motor energizing circuit, means for energizing said circuit,

. a timing device responsive to the expiration of a fails to complete a working stroke.

4. In a feeding and injection device, an injector chamber, an injection ,member therein, a feeding chamber in commimication with said injector chamber, a movable feeding member in said feeding chamber, a feeding motor connected to said feeding member for moving said feeding member, a circuit for energizing said feeding motor, means responsive to a predetermined motion of said injection member for energizing said feeding motor circuit, and a timing device responsive to the expiration of a predetermined period of time after the energization of said feeding motor circuit 'for deenergizlng said feeding motor circuit whereby to feed a predetermined quantityof material to said injector chamber.

5. In a feeding and injection device, an intion of said injection member for energizing said feeding motor circuit, and a timing device responsive to the expiration of a predetermined period of time after the energization of said feeding motor circuit for deenergizing said feeding motor circuit whereby to feed a. predetermined quantity of material to said injector chamber, said timing means being connected to operate said feeding motor to supply a quantity of feeding material slightly in excess of the quantity required by said injector chamber, andsaid feeding-motor-energizing means being rendered inoperative in response to an incomplete stroke of said injection member, whereby to cause the accumulation of a predetermined quantity of surplus material to effect a skip cycle of operation of said feeding motor.

6. In a feeding and injection device, an injector chamber, an injection member therein, a feeding chamber in communication with said. injector chamber, a movable feeding member in said feeding chamber, a feeding motor connected to said feeding member for moving said feeding member, a circuit for energizing said feeding motor, and a single limit switch in said circuit positioned to be operated to energize said feeding motor circuit in response to the execution of a substantially complete injection stroke of said injection member.

7. In a feeding and injection device, an injector chamber, an injection member therein, a

feeding chamber in communication with said injector chamber, a movable feeding member in said feeding chamber, a feeding motor connected to said feeding member for moving said feeding member, a circuit for energizing said feeding motor, a limit switch in said circuit positioned to be operated to energize said feeding motor circuit'in response to the execution of a substantially complete injection stroke of said injection member, and a timing device responsive to the expiration of a predetermined period of time after the energization of said feeding motor circuit for deenergizing said circuit, whereby, to feed a predetermined quantity of material to said injector chamber.

8. In a feeding and injection device, an injector chamber, an injection member therein, a feeding chamber in communication with said injector chamber, a movable feeding member in said feeding chamber, a feeding motor connected to said feeding member for moving said feeding member, a circuit for energizing said feeding motor, and a single limit switch connected to control the energization of said feeding motor circuit and positioned to be shifted to energize said feeding motor circuit to execute a feeding cycle in response to the substantial completion of a stroke of said injection member.

9. In a feeding and injection device, an injector chamber, an injection member therein, a feeding chamber in communication with said injector chamber, a movable feeding member in said feeding chamber, a feeding motor connected to said feeding member for moving said feeding member, a circuit for energizing said feeding motor, and a single limit switch connected to control the energization of said feeding motor circuit and positioned to be shifted to energize said feeding motor circuit to execute a feeding cycle solely when said injection member substantially completes an injection stroke.

IRA B. LAWYER. 

